/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_conv_opt_q7.c
 * Description:  Convolution of Q7 sequences
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
  @ingroup groupFilters
 */

/**
  @addtogroup Conv
  @{
 */

/**
  @brief         Convolution of Q7 sequences.
  @param[in]     pSrcA      points to the first input sequence
  @param[in]     srcALen    length of the first input sequence
  @param[in]     pSrcB      points to the second input sequence
  @param[in]     srcBLen    length of the second input sequence
  @param[out]    pDst       points to the location where the output result is written.  Length srcALen+srcBLen-1.
  @param[in]     pScratch1  points to scratch buffer(of type q15_t) of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.
  @param[in]     pScratch2  points to scratch buffer (of type q15_t) of size min(srcALen, srcBLen).
  @return        none

  @par           Scaling and Overflow Behavior
                   The function is implemented using a 32-bit internal accumulator.
                   Both the inputs are represented in 1.7 format and multiplications yield a 2.14 result.
                   The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
                   This approach provides 17 guard bits and there is no risk of overflow as long as <code>max(srcALen, srcBLen)<131072</code>.
                   The 18.14 result is then truncated to 18.7 format by discarding the low 7 bits and then saturated to 1.7 format.
 */

void arm_conv_opt_q7(
	const q7_t *pSrcA,
	uint32_t srcALen,
	const q7_t *pSrcB,
	uint32_t srcBLen,
	q7_t *pDst,
	q15_t *pScratch1,
	q15_t *pScratch2)
{
	q15_t *pScr1 = pScratch1;                      /* Temporary pointer for scratch */
	q15_t *pScr2 = pScratch2;                      /* Temporary pointer for scratch */
	q15_t x4;                                      /* Temporary input variable */
	q15_t *py;                                     /* Temporary input2 pointer */
	q31_t acc0, acc1, acc2, acc3;                  /* Accumulators */
	const q7_t *pIn1, *pIn2;                             /* InputA and inputB pointer */
	uint32_t j, k, blkCnt, tapCnt;                 /* Loop counter */
	q31_t x1, x2, x3, y1;                          /* Temporary input variables */
	const q7_t *px;                                      /* Temporary input1 pointer */
	q7_t *pOut = pDst;                             /* Output pointer */
	q7_t out0, out1, out2, out3;                   /* Temporary variables */

	/* The algorithm implementation is based on the lengths of the inputs. */
	/* srcB is always made to slide across srcA. */
	/* So srcBLen is always considered as shorter or equal to srcALen */
	if (srcALen >= srcBLen) {
		/* Initialization of inputA pointer */
		pIn1 = pSrcA;

		/* Initialization of inputB pointer */
		pIn2 = pSrcB;
	} else {
		/* Initialization of inputA pointer */
		pIn1 = pSrcB;

		/* Initialization of inputB pointer */
		pIn2 = pSrcA;

		/* srcBLen is always considered as shorter or equal to srcALen */
		j = srcBLen;
		srcBLen = srcALen;
		srcALen = j;
	}

	/* points to smaller length sequence */
	px = pIn2 + srcBLen - 1;

	/* Apply loop unrolling and do 4 Copies simultaneously. */
	k = srcBLen >> 2U;

	/* First part of the processing with loop unrolling copies 4 data points at a time.
	 ** a second loop below copies for the remaining 1 to 3 samples. */
	while (k > 0U) {
		/* copy second buffer in reversal manner */
		x4 = (q15_t) * px--;
		*pScr2++ = x4;
		x4 = (q15_t) * px--;
		*pScr2++ = x4;
		x4 = (q15_t) * px--;
		*pScr2++ = x4;
		x4 = (q15_t) * px--;
		*pScr2++ = x4;

		/* Decrement loop counter */
		k--;
	}

	/* If the count is not a multiple of 4, copy remaining samples here.
	 ** No loop unrolling is used. */
	k = srcBLen % 0x4U;

	while (k > 0U) {
		/* copy second buffer in reversal manner for remaining samples */
		x4 = (q15_t) * px--;
		*pScr2++ = x4;

		/* Decrement loop counter */
		k--;
	}

	/* Fill (srcBLen - 1U) zeros in scratch buffer */
	arm_fill_q15(0, pScr1, (srcBLen - 1U));

	/* Update temporary scratch pointer */
	pScr1 += (srcBLen - 1U);

	/* Copy (srcALen) samples in scratch buffer */
	/* Apply loop unrolling and do 4 Copies simultaneously. */
	k = srcALen >> 2U;

	/* First part of the processing with loop unrolling copies 4 data points at a time.
	 ** a second loop below copies for the remaining 1 to 3 samples. */
	while (k > 0U) {
		/* copy second buffer in reversal manner */
		x4 = (q15_t) * pIn1++;
		*pScr1++ = x4;
		x4 = (q15_t) * pIn1++;
		*pScr1++ = x4;
		x4 = (q15_t) * pIn1++;
		*pScr1++ = x4;
		x4 = (q15_t) * pIn1++;
		*pScr1++ = x4;

		/* Decrement loop counter */
		k--;
	}

	/* If the count is not a multiple of 4, copy remaining samples here.
	 ** No loop unrolling is used. */
	k = srcALen % 0x4U;

	while (k > 0U) {
		/* copy second buffer in reversal manner for remaining samples */
		x4 = (q15_t) * pIn1++;
		*pScr1++ = x4;

		/* Decrement the loop counter */
		k--;
	}

	/* Fill (srcBLen - 1U) zeros at end of scratch buffer */
	arm_fill_q15(0, pScr1, (srcBLen - 1U));

	/* Update pointer */
	pScr1 += (srcBLen - 1U);

	/* Temporary pointer for scratch2 */
	py = pScratch2;

	/* Initialization of pIn2 pointer */
	pIn2 = (q7_t *) py;

	pScr2 = py;

	/* Actual convolution process starts here */
	blkCnt = (srcALen + srcBLen - 1U) >> 2U;

	while (blkCnt > 0) {
		/* Initialze temporary scratch pointer as scratch1 */
		pScr1 = pScratch1;

		/* Clear Accumlators */
		acc0 = 0;
		acc1 = 0;
		acc2 = 0;
		acc3 = 0;

		/* Read two samples from scratch1 buffer */
		x1 = read_q15x2_ia(&pScr1);

		/* Read next two samples from scratch1 buffer */
		x2 = read_q15x2_ia(&pScr1);

		tapCnt = (srcBLen) >> 2U;

		while (tapCnt > 0U) {
			/* Read four samples from smaller buffer */
			y1 = read_q15x2_ia(&pScr2);

			/* multiply and accumlate */
			acc0 = __SMLAD(x1, y1, acc0);
			acc2 = __SMLAD(x2, y1, acc2);

			/* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			/* multiply and accumlate */
			acc1 = __SMLADX(x3, y1, acc1);

			/* Read next two samples from scratch1 buffer */
			x1 = read_q15x2_ia(&pScr1);

			/* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x1, x2, 0);
#else
			x3 = __PKHBT(x2, x1, 0);
#endif

			acc3 = __SMLADX(x3, y1, acc3);

			/* Read four samples from smaller buffer */
			y1 = read_q15x2_ia(&pScr2);

			acc0 = __SMLAD(x2, y1, acc0);

			acc2 = __SMLAD(x1, y1, acc2);

			acc1 = __SMLADX(x3, y1, acc1);

			x2 = read_q15x2_ia(&pScr1);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			acc3 = __SMLADX(x3, y1, acc3);

			/* Decrement loop counter */
			tapCnt--;
		}

		/* Update scratch pointer for remaining samples of smaller length sequence */
		pScr1 -= 4U;

		/* apply same above for remaining samples of smaller length sequence */
		tapCnt = (srcBLen) & 3U;

		while (tapCnt > 0U) {
			/* accumlate the results */
			acc0 += (*pScr1++ * *pScr2);
			acc1 += (*pScr1++ * *pScr2);
			acc2 += (*pScr1++ * *pScr2);
			acc3 += (*pScr1++ * *pScr2++);

			pScr1 -= 3U;

			/* Decrement loop counter */
			tapCnt--;
		}

		blkCnt--;

		/* Store the result in the accumulator in the destination buffer. */
		out0 = (q7_t)(__SSAT(acc0 >> 7U, 8));
		out1 = (q7_t)(__SSAT(acc1 >> 7U, 8));
		out2 = (q7_t)(__SSAT(acc2 >> 7U, 8));
		out3 = (q7_t)(__SSAT(acc3 >> 7U, 8));

		write_q7x4_ia(&pOut, __PACKq7(out0, out1, out2, out3));

		/* Initialization of inputB pointer */
		pScr2 = py;

		pScratch1 += 4U;
	}

	blkCnt = (srcALen + srcBLen - 1U) & 0x3;

	/* Calculate convolution for remaining samples of Bigger length sequence */
	while (blkCnt > 0) {
		/* Initialze temporary scratch pointer as scratch1 */
		pScr1 = pScratch1;

		/* Clear Accumlators */
		acc0 = 0;

		tapCnt = (srcBLen) >> 1U;

		while (tapCnt > 0U) {
			acc0 += (*pScr1++ * *pScr2++);
			acc0 += (*pScr1++ * *pScr2++);

			/* Decrement loop counter */
			tapCnt--;
		}

		tapCnt = (srcBLen) & 1U;

		/* apply same above for remaining samples of smaller length sequence */
		while (tapCnt > 0U) {
			/* accumlate the results */
			acc0 += (*pScr1++ * *pScr2++);

			/* Decrement loop counter */
			tapCnt--;
		}

		blkCnt--;

		/* Store the result in the accumulator in the destination buffer. */
		*pOut++ = (q7_t)(__SSAT(acc0 >> 7U, 8));

		/* Initialization of inputB pointer */
		pScr2 = py;

		pScratch1 += 1U;
	}

}

/**
  @} end of Conv group
 */
